Intersting how a simple question like "What is the difference between psig and psia?" can trigger off much discussion.

I've never been comfortable with the term "back pressure".

To me, a pressure just exists and doesn't point forwards or backwards. Does anyone have a clear definition of the term?

Back pressure is the pressure measured at the discharge side of the pump, it is caused by the resistance the system (piping) generates agains the passage of fluid.

I agree with vesselguy.  I have ordered a few safety valves in my time.

What about a back-pressure turbine?  Dont they exist?

If you are confused about back-pressure and dont think it exists, I think you should get out more.

Perhaps it is a term misused rather than a term that doesnt exist.

I totally agree with you on not using the term "back pressure" as if it is an offical engineering term.  I have never seen this term used in any of my University text books.  I encountered this term only when come out to work.  At first, I thought what hell does it imply, but then I gotten to "understand" it by investigating the P&ID and nearby equipment and then the light bulb turned on.  I guess the use of this term is faster than saying "overcome an existing pressure at xxx of xxx psi", but far less exacting.

Sad to say, we Engineers are inventing new terms every year.  Just this month, I was taking over a simple double wall tank package from a young Project Engineer.  I looked into the NDE he specified to the Vendors and I saw "Incis test".  I thought what the hell is this.  In my 14 years working on tanks, vessels and exchangers I have never heard of such test.  But inside, I have stinking suspicion that he means Interstitial Vacuum Test.  Sure enough that's what it is. He made it up and the young lad thinks I don't know and starts explaining it in detail to me.

So, whatever terms we get hit with in this bussiness, we should ask the person who threw the term at you and find out exactly what he/she means.  Asking anybody else could leave you in a worst state than you started off at.

MORE NEWS